The Popcoin API is a service that developers install into their own systems to generate variable usage costs at as micro or macro a level as they desire. It's available in JSON format with access token as the authentication method. Popcoin is a metered billing service for developers.
The following is a list of how-to and tutorial content that matched your search term. ProgrammableWeb's how-to content comes from two sources; full-blown tutorials that we publish ourselves and other highly relevant tutorials that we find elsewhere on the Web. This list represents on combination of both tutorial types and if you go to ProgrammableWeb's API University, you'll not only be able to find more, they are organized based on your role (API providers or developers who consumes APIs). If you know of a tutorial that would be of interest to the ProgrammableWeb community, we'd like to know about it. Be sure to check our guidelines for making contributions to ProgrammableWeb.